Dry cooling system using thermally induced vapor polymerization

ABSTRACT

A system and method for providing dry cooling of a source liquid, having a plurality of heat exchangers which depolymerize and polymerize a polymer. Specifically, the depolymerization process is endothermic and draws heat from a source liquid in a first heat exchanger, and the polymerization process is exothermic and expels heat from a second heat exchanger. Additional heat exchangers and holding tanks may be incorporated in the system and method. In some embodiments the system further provides additional cooling of the polymer prior to depolymerization using cooler night ambient air.

BACKGROUND OF THE DISCLOSED TECHNOLOGY

The disclosed technology regards a cooling system which can function toprovide power plant condensers with cooling water at desirabletemperature levels to maintain turbine power production at optimumthermal efficiency levels. The technology may also replace the powerplant condenser, and provide the power plant low-pressure-turbine withreturn water at temperatures to achieve the turbine's designed optimumback pressure at any ambient conditions. The disclosed technologyfurther relates to an improvement in dry cooling systems to overcome theinherent thermodynamic performance penalty of air-cooled systems,particularly under high ambient temperatures. The disclosed technologyhas other applications, including providing cooling and heating in airconditioning systems, and generally in the removal of heat from liquidsources in a controlled environment, as well as streams or other watersources in the natural environment. Using the methods of the technology,heat generated by the system may also be used to warm an environment oranother liquid source.

More than 86% of electricity in the United States of America is producedby thermoelectric power generating plants, most of which use coal,natural gas, or nuclear fuel to generate thermal energy. As shown inFIG. 1, the thermal energy produces superheated steam in theboiler/steam generator, which drives a steam turbine to produceelectrical power by the generator. Each power plant is designed for theconditions of its particular geographic location, which conditionsimpact the design point of the low pressure turbine exhaust pressure.The exhausted steam coming out of the turbine last stage is condensed ina condenser by cooling heat transfer with the condenser, then pumpedback to the boiler as boiler return water, and the process is repeated.Although unique to each plant, the return condensate water ranges intemperature from 35° C. to 52° C.

The pressure of the outlet steam causing the turbine blade rotation,called back pressure, is defined by the condenser temperature. For drycooling systems, the condenser temperature is a strong function of theambient temperature. Therefore, an increase in ambient temperaturedirectly affects the power plant efficiency. For indirect coolingsystems, the ambient air increases the cooling water temperature whichin turn increases the condenser temperature. However, for direct aircooled systems the condenser temperature is directly influenced by theambient temperature.

Typically, more than 60% of the original energy generated by the steamgenerator/boiler is wasted and carried away as low-grade heat by theplant condenser cooling water or directly dissipated to the ambient air.Operators must remove this heat, and 99% of baseload thermoelectricplants in the United States of America use water-cooled systems, or wetcooling, to remove the heat from the condenser cooling water. Powerplant operators prefer wet cooling over dry-cooling systems becauseambient water temperatures tend to be cooler and more stable thanambient air temperatures; further, water evaporation allows foradditional cooling capacity, enabling more cost-effective rejection ofheat. However, the wet cooling processes lead to a significant amount ofwater loss, with power plants using wet-cooling systems currentlyaccounting for 41% of all fresh water withdrawals in the United Statesof America.

Availability of fresh water resources is increasingly strained bydrought and growing demands, and potential climate change impacts adduncertainty to the quality and quantity of future water supplies.However, while dry-cooling technologies do not result in significantwater use, because of their sensitivity to ambient air temperaturescurrent dry-cooling technologies drive down the overall efficiency ofpower generation compared with the efficiency of wet cooled condensers.Therefore, there is a need for a dry-cooling technology that eliminateswater loss or the dependency on water while maintaining the highoperating efficiencies of electric power generation presently achievedby wet-cooling technologies.

Power plant condenser cooling is divided into five main technologyareas, which differ greatly in the amounts of water consumed: (1)once-through cooling; (2) closed-cycle wet cooling; (3) cooling ponds;(4) dry cooling; and (5) hybrid cooling.

Once-through cooling systems withdraw cold water from, and return heatedwater to, a natural body of water such as a lake, a river, or the ocean.In operation, the source water is pumped through the tubes of a steamcondenser. As steam from the turbine condenses on the outside of thetubes, the heat of condensation is absorbed by the source water flowingthrough the tubes. The source water exiting the condenser, warmed by 15°F. to 30° F. depending on system design, is discharged to the originalsource. The amount withdrawn varies from 25,000 to 50,000 gallons/MWh.Although none of the water is consumed within the plant, someconsumptive loss results from enhanced evaporation from the surface ofthe natural body of water due to the heated water discharge. The lossdue to this enhanced evaporation is not well known and is expected to besite-specific, but it has been estimated as 0.5% to 2% of the withdrawnsource water amount, or 125 to 1000 gallons/MWh. The biggest drawback ofonce-through cooling systems is that heated discharges may degrade thenatural body of water, increasing the overall water temperature of thenatural body of water. The thermal pollution is most significant whenthe source of the water is a river or other body with limited volume,where the water withdrawn and discharged is a significant portion of thenatural water flow.

Closed-cycle wet cooling is similar to once-through cooling in that ascold source water flows through the tubes of a steam condenser, steamfrom the turbine condenses on the outside of the tubes. However, insteadof returning the heated condenser water to its source, it is pumped to awet cooling device such as a cooling tower, cooling pond, or coolingcanal, where it is cooled by evaporation of a small portion of the waterto the atmosphere to within 5° F. to 10° F. of the ambient wet-bulbtemperature. Makeup water is added to compensate for the water loss dueto evaporation and the again cooled water is then recirculated to thesteam condenser.

Wet cooling devices used in closed-cycle wet cooling transfer thermalenergy from heated cooling water to the atmosphere through both heattransfer to the ambient air and evaporation, to bring the cooling waterto near wet-bulb air temperature. Specifically, as ambient air is drawnpast a flow of cooling water, a small portion of the water evaporates,and the energy required to evaporate that portion of the water is takenfrom the remaining mass of water, thus reducing its temperature. About970 Btu of thermal energy is absorbed for each pound of waterevaporated.

To achieve better performance, heated cooling water may be sprayed to amedium, called fill, to increase the surface area and the time ofcontact between the air and water flow. Some systems use splash fill,which is material placed to interrupt the water flow causing splashing.Other systems use film fill, which includes thin sheets of material(usually PVC) upon which the water flows, enhancing evaporation.

Cooling towers draw air either by natural draft or mechanical draft, orboth. Natural draft cooling towers utilize the buoyancy of warm air, anda tall chimney structure. In this structure the warm, moist airnaturally rises due to the density differential compared to the dry,cooler outside air, producing an upward current of air through thetower. Hyperbolic towers have become the design standard for naturaldraft cooling towers due to their structural strength and minimum usageof material. The hyperbolic shape also aids in accelerating air flowthrough the tower, and thus increases cooling efficiency. Mechanicaldraft towers use motor-driven fans to force or draw air through thetowers, and include induced draft towers which employ a fan at the topof the tower that pulls air up through the tower (as shown in FIG. 1),and forced draft towers which use a blower-type of fan at the bottom ofthe tower, which forces air into the tower.

Cooling ponds are man-made bodies of water which supply cooling water topower plants, and are used as an effective alternative to cooling towersor once-through cooling systems when sufficient land, but no suitablenatural body of water, is available. The ponds receive thermal energyfrom the heated condenser water, and dissipate the thermal energy mainlythrough evaporation. The ponds must be of sufficient size to providecontinuous cooling, and makeup water is periodically added to the pondsystem to replace the water lost through evaporation.

Current dry cooling systems can be a direct system, in which turbineexhaust steam is condensed in an air-cooled condenser (ACC), or anindirect system, in which the steam is condensed in a conventionalwater-cooled condenser. For indirect systems, the heated cooling wateris circulated through an air-cooled heat exchanger before returning tothe water-cooled condenser. In the direct system, the steam is condensedin the ACC in finned tube bundles (galvanized steel tubes with aluminumfins), and the heat is dissipated directly to the ambient air. Directand indirect cooling systems operate without water loss (other than asmall amount of water used to periodically clean the air-side surfacesof the air-cooled condenser or heat exchanger). The condensingtemperature, in the case of direct dry cooling, or the cold watertemperature, in the case of indirect dry cooling, is limited by theambient air temperature, which is always higher than the ambientdry-bulb temperature. Although dry cooling achieves significant watersavings, the capital and operating costs are much higher than they arefor closed-cycle wet cooling, and the physical footprint is larger.Furthermore, plant performance is reduced in the hotter times of theyear when the steam-condensing temperature (and hence the turbineexhaust pressure) is substantially higher (being limited by ambient airtemperature) than it would be with wet cooling.

Another dry cooling system is the Heller System, which uses a directcontact condenser instead of a steam surface condenser. In this systemthe turbine exhaust steam is in direct contact with a cold water spray,and no condenser tubes are used. The resulting hot condensate and watermixture are pumped to an external air-cooled heat exchanger. Theair-cooled heat exchanger may have a mechanical draft design, a naturaldraft design or a fan-assisted natural draft design. The direct contactcondenser has the advantage of lower terminal temperature difference(TTS, which is the temperature difference between the saturation steamtemperature and the cooling water outlet temperature), and thus lowerturbine back-pressure.

Hybrid cooling systems have both dry and wet cooling elements that areused alternatively or together to achieve the best features of eachsystem. In a hybrid cooling system a power plant can achieve the wetcooling performance on the hottest days of the year, and the waterconservation capability of dry cooling at other times. The wet and drycooling components can be arranged in series, or in parallel, and may beseparate structures or integrated into a single tower. The dry coolingsystem elements can be either direct or indirect types. The most commonconfiguration for hybrid cooling systems to date has been parallel,separate structures with direct dry cooling.

Like the wet cooling systems described hereinabove, the wet coolingelements of a hybrid system use significant amounts of water,particularly during the summer months. Therefore, it is most suitablefor sites that have significant water availability but not enough forall-wet cooling at all times of the year. For sites where water use ishighly limited or contentious, even the use of 20% of the all-wetamounts might be unacceptable, requiring all-dry cooling to allow theplant to be permitted. For sites with adequate water, the performanceand economic advantages of all-wet cooling systems are significant. Insome cases, plant siting might be eased by evidence of “responsiblecitizenship,” in which by means of a hybrid cooling system a plantdeveloper offers some degree of reduced water use to the local communityconcerned about water for agriculture, recreation, or industry.

The disclosed technology overcomes the aforementioned problemsassociated with power plant condenser cooling. A broad object of thedisclosed technology is to provide a novel method and apparatus forremoval of waste heat from power plant condensers with high overallprocess thermal efficiency and without water waste.

Another object of the disclosed technology is to provide for power plantcooling in a relatively compact apparatus, by maximizing the thermalcapacities of the apparatus. A further object of the disclosedtechnology is to provide a dry cooling system and method of dry coolingfor effective heat removal or heat generation, operating at a highcoefficient of performance.

General Description of the Disclosed Technology

In accordance with the above objects, the disclosed technology relatesto cooling systems and methods which function to provide power plantcondensers with return water at the necessary temperature levels tomaintain power production at their optimum thermal efficiency levels.Optimum condenser temperature varies depending on the power plant'sdesign and its geographic location. Condenser temperature design forcombined cycle and steam power plants ranges between 35-52° C. Ashereinabove discussed, the condenser's ability to lower supplywater/condensate temperature determines the back pressure for thelow-pressure steam turbine, wherein an increase in condenser temperatureincreases the back pressure on the turbine blades, leading to reducedpower plant efficiency.

The disclosed technology may also replace the power plant condenser, orbe used to improve other dry cooling systems. The disclosed technologyfurther may be used in other applications, such as providing cooling andheating in air conditioning systems, and generally in the removal ofheat from waste/stream heat sources.

The disclosed technology is specifically useful in a power plant's drycooling system, using the depolymerization of a polymer over a catalystin a closed system, including in liquid communication a plurality ofheat exchangers configured to form depolymerization and polymerizationassemblies. In some embodiments a cold energy storage assembly is alsoprovided.

The depolymerization process and assembly of the disclosed technologydepolymerizes a polymer over a catalyst, resulting in a monomer richvapor. This depolymerization process is an endothermic reaction, drawingheat from the source water (e.g., condenser water or steam exiting thelow pressure turbine, last stage) flowing through the heat exchanger ina depolymerization cooling unit (DCU).

The monomer rich vapor is then transferred to the polymerizationassembly, reacting over an acid catalyst bed in a polymer heating unit(PHU) to convert the monomer back to the original polymer in liquidphase. The polymerization process is an exothermic reaction, and heatgenerated may be expelled from the heat exchanger vessel of thepolymerization assembly by either air cooled or liquid cooled processes.In some embodiments, the polymerization assembly employs the dry coolingapproach to expel heat from the PHU, using air cooled heat exchangers.To complete the cycle, the polymer stream is pumped by a liquid pumpback to the DCU to provide below ambient wet bulb temperature coolingfor a standalone cooling system.

To achieve continuous operation with high conversion efficiencies, thesystem may include one or more polymer separation units (PSU), wherebyusing heat from an independent stream of source liquid or ambient air,the monomer vapor rich mixture from the DCU and/or the polymer richliquid mixture from the PHU are further separated into two streams: avaporous light monomer rich stream and a liquid polymer rich stream. ThePSU(s) thereby creates a buffer between the DCU and the PHU. In someembodiments a single PSU is placed downstream of the DCU and downstreamfrom the PHU, enhancing polymer/monomer separation from each assembly.In another embodiment, a first PSU can be placed downstream of the DCU,enhancing polymer-monomer separation from the DCU product vapor stream,and a second PSU is placed downstream of the PHU, enhancingpolymer-monomer separation from the PHU product liquid stream. In eitherof these configurations, the light monomer-rich stream from the PSU(s)is circulated into the PHU for further polymerization reaction, whilethe polymer-rich liquid stream from the PSU(s) is circulated directly tothe DCU for depolymerization, or collected in a holding tank for latercirculation through the DCU.

To provide cooling below ambient wet bulb temperatures during hot summerdays with temperatures higher than the saturation temperature at steamturbine back pressure, the elevated temperature polymer produced in thePHU may be stored in a cold energy storage assembly, having a daystorage tank (DST) which stores the elevated temperature polymer fromthe PHU (or the PSU). In the evening, the elevated temperature polymercycles through a polymer cooling heat exchanger unit (PCU), dissipatingits sensible heat into the cooler evening ambient air. The lowertemperature polymer may then be stored in a cold energy storage tank(CST), where it waits for reuse the next day by pumping the liquidpolymer to the DCU, and the cycle is repeated.

In some embodiments, water is incorporated into thedepolymerization/polymerization cycle of the disclosed technology,partially vaporizing in the DCU with the depolymerization of thepolymer, and condensing in the PHU with the polymerization of themonomer,

For optimal performance, the polymer should be selected based on thetemperature range in which it depolymerizes and polymerizes, wherein inthe power plant condenser cycle the temperature range ofdepolymerization is comparable with the power plant's cooling systemoperating temperatures, and the temperature range of polymerizationexceeds the hottest ambient air summer temperatures at the site. Othertemperature ranges may be suitable in other applications, and thereforeother polymers may be more suitable.

In an exemplary embodiment of the disclosed technology, the liquidpolymer is paraldehyde, which is depolymerized in the DCU into the lightmonomer acetaldehyde over an acid based catalyst. The acetaldehyde richvapor, having a small amount of paraldehyde gas, is actively removedfrom the DCU as vapor using a blower, compressor or vacuum pump. Thisactive removal of acetaldehyde rich vapor allows the paraldehyde to bedepolymerized beyond its chemical equilibrium. The depolymerization andresulting vaporization process are endothermic, resulting in heatabsorption from the source liquid flowing through the heat exchanger ofthe DCU. The maximum coolant specific energy, estimated based on 100%depolymerization conversion, is 1,434 kJ/kg. In practical operation, thedepolymerization process can be controlled by varying operatingparameters with high conversion up to 95%, providing a coolant specificenergy up to 1,363 kJ/kg to meet cooling needs. This practical coolantspecific energy is up to 4 times of the latent heat storage capacity ofice.

The monomer conversion of acetaldehyde in the polymerization process ofthe PHU is typically between 60-80%, depending on the processtemperature (e.g., ambient air temperature for an air cooled heatexchanger). However, as hereinabove discussed remaining light and liquidmonomer can be separated from the polymer rich liquid in the PSU, andexcess light monomer can be recycled back to the polymerizationassembly. With this recycling, the overall monomer conversion may reach95%. Thereby, the exothermic process has polymerization conversions thatmatch the depolymerization conversions for the endothermic process,allowing the cycle to be operated continuously and efficiently as a heatpump cycle by removing heat from the cooling process, and rejecting thatheat from the heating process, with overall coolant energy density up to1,363 kJ/kg.

The disclosed technology further provides a process for an efficient drycooling system to dissipate low quality heat from chemical, mechanical,thermal, or power plant operations. It can work as a standalone system,or be synchronized with other dry cooling units. Further, it iscontemplated that the exothermic polymerization process may be used as aheat source for other processes or purposes, such as for example adistillation unit.

The cycle of the disclosed technology operates based on chemical heatpump fundamentals and utilizes chemical thermal energy storage.Therefore, it is more tolerant to ambient temperature fluctuation thantraditional dry cooling technology such as air cooled heat exchangers.For example, at an ambient temperature of 45° C., air cooling of a 45°C. water stream is impossible since there is no driving force for theheat transfer between water and air. With the cycle of the disclosedtechnology at the same ambient temperature condition, the endothermicprocess will lower the coolant/polymer temperature, allowing heattransfer between the water and the coolant. Using paraldehyde as thepolymer, even under conditions when the coolant/polymer is fed attemperatures higher than the hottest ambient temperatures, the coolantperformance will observe less than 1.4% performance penalty per 10° C.increase in polymer temperature. This behavior is caused by the smallratio between the paraldehyde sensible heat capacity and the overallreaction specific enthalpy change. Specifically, the sensible heatcapacity for paraldehyde is 0.27 kJ/mol/C; therefore, the sensible heatstorage for 10° C. temperature change is only 2.7 kJ/mol, which onlyaccounts for 1.4% of total reaction heat (189.5 kJ/mol). For example theincrease in the polymer temperature from 25-35° C. reduces the DCUcooling capacity by 1.4% (a polymer feed at 25° C. gives a DCU coolingcapacity of 1 kW; when its temperature increases to 35° C., its coolingcapacity is reduced to 0.986 kW). Similarly, the monomer will regeneratein the polymerization process with a process temperature higher than theambient 45° C. temperature, allowing heat to be rejected to theenvironment using a traditional air cooled heat exchanger. Thus, thecycle of the disclosed technology allows the system to provide efficientcooling at high ambient temperatures, when traditional dry coolingmethods fail.

FIGURES

Embodiments of the invention will now be described in conjunction withthe accompanying drawings, where:

FIG. 1 is a flow diagram of a prior art thermoelectric coal or naturalgas fire steam power plant, using a cooling tower wet cooling system.

FIG. 2 is a flow diagram of a thermoelectric coal or natural gas firesteam power plant, including an embodiment of the apparatus of thedisclosed technology in an indirect dry cooling configuration.

FIG. 3 is a flow diagram of a thermoelectric coal or natural gas firesteam power plant, including an embodiment of the apparatus of thedisclosed technology in a direct dry cooling configuration.

FIG. 4 is a schematic process flow diagram of an embodiment of theapparatus of the disclosed technology, using cold energy storage.

FIG. 5 is a schematic process flow diagram of another embodiment of theapparatus of the disclosed technology as an uninterrupted cooling cycle,without cold energy storage.

FIG. 6 is a schematic process flow diagram of another embodiment of theapparatus of the disclosed technology, using an uninterrupted heatpumpin the cooling cycle.

FIG. 7 is a schematic process flow diagram of the embodiment of FIG. 6,in the heating cycle.

FIG. 8 is a schematic process flow diagram of an embodiment of theapparatus of the disclosed technology, using two PSUs.

FIG. 9 is a schematic process flow diagram of another embodiment of theapparatus of the disclosed technology.

FIG. 10 is a schematic process flow diagram of another embodiment of theapparatus of the disclosed technology, using an uninterrupted heatpumpin the cooling cycle.

FIG. 11 is a schematic process flow diagram of the embodiment of FIG.10, in the heating cycle.

DETAILED DESCRIPTION OF THE DISCLOSED TECHNOLOGY

The features and principles of the disclosed technology are described indetails and through embodiments below, with reference to the indicatedfigures. The particular embodiments of the disclosed technology arepresented as examples, and should not be understood as limitations ofthe claimed inventions. The novel features of the disclosed technologycan be employed as numerous embodiments within the scope of thedisclosed technology. Additional heat exchangers, pressure regulatingcontrol devices, and other ancillary equipment necessary for operationof the disclosed technology in accordance with the teachings of thisdisclosure, the use of which are well known in the art, are not shown inthe schematic figures. A person skilled in the art may readily see thatvarious configurations of heat exchangers, pumps, blowers and otherstandard processing equipment may be employed to achieve desired processstream temperatures and pressures, while maximizing the overall processthermal efficiency.

The present technology uses a depolymerization and polymerizationthermochemical cycle to provide dry cooling to a condenser or otherwater source, eliminating water losses and maintaining power plantthermal efficiency even during the hottest time of the year. One ofpolymers suitable for use in the disclosed technology is paraldehyde,which depolymerizes to the monomer acetaldehyde. Other systems may usepolymers with higher depolymerization temperatures when appropriate forpurposes of the system, for example when the system is used to cool lowquality waste heat streams (<200° C.).

The disclosed technology uses polymerization [paraldehyde(Pa(I):C₆H₁₂O₃(I)], depolymerization [acetaldehyde (A(I):CH₃CHO)] andvaporization [acetaldehyde ((A(g):CH₃CHO))] thermochemical reactionscycle for cooling purposes. The equations representing the chemicalreaction of the depolymerization of paraldehyde and vaporization ofacetaldehyde are indicated in equations 1 and 2:C₆H₁₂O₃(I)

3CH₃CHO(I), ΔH_(298K)=110.3 kJ/mol  (1)3 CH₃CHO(I)

3 CH₃CHO(g), ΔH_(298K)=79.2 kJ/mol  (2)The net reaction is then:C₆H₁₂O₃(I)

3 CH₃CHO(g), ΔH_(298K)=189.5 kJ/mol  (3)

One mole of liquid paraldehyde is depolymerized over an acid catalyst,into three moles of gaseous acetaldehyde. The depolymerization reactionis endothermic with a net reaction heat of 189.5 kJ/mol (as the sum ofreaction heat and vaporization heat).

Although the depolymerization reaction is reversible, it is promoted bythe vaporization and removal of the monomer. Specifically, in a typicaldepolymerization reaction without the active removal of light monomer,the reaction will start first by depolymerizing the polymer to producelight monomer. However, because this is a reversible reaction, as thepolymer is being depolymerized, the produced light monomer will try toconvert (re-polymerize) back to the polymer. The depolymerization andre-polymerization rates depend on the concentration of the polymer andthe light monomer in the liquid at a given temperature and pressure. Ingeneral, higher concentrations will result in a faster reaction rate.Therefore, high polymer concentration will lead to a highdepolymerization rate and high light monomer concentration will lead toa high re-polymerization rate. Eventually, both polymer and lightmonomer concentrations in the liquid will reach a state where thedepolymerization and re-polymerization rate are equal and the polymerand monomer concentrations will remain constant. Thus thedepolymerization conversion is limited by the reaction equilibrium.

At the equilibrium state, the resulting mixture is a liquid and themonomer (having a very low boiling point as compared to the polymer)will slowly evaporate from the liquid mixture. Actively removing themonomer rich vapor from the DCU (by means of a blower, for example)creates a low pressure environment, accelerating the evaporation rate ofthe monomer. As the light monomer concentration decreases (through bothremoval of the monomer and additional polymer feed), thedepolymerization reaction dominates to produce more light monomer toreach the equilibrium.

For example, at 40° C., the equilibrium polymer and light monomerconcentrations are about 83 wt % and 17 wt % in liquid, respectively. Ifpure polymer is fed to the DCU and evaporation is negligible, theoverall depolymerization conversion is calculated based on liquidcomposition (17%). By equalizing the evaporation rate (by removal of themonomer rich vapor) and the polymer feed rate, the overalldepolymerization conversion is calculated based on the vaporcomposition. If the vapor composition is 90 wt % of light monomer(average light monomer composition under test conditions), the overalldepolymerization conversion is 90%. Thus, by active removal of themonomer from the reaction tank the overall depolymerization conversionis significantly higher than the equilibrium conversion.

The system of the disclosed technology utilizes the high reaction heatof the depolymerization of paraldehyde for cooling a source liquid. Withits net reaction heat of 189.5 kJ/mol, the heat capacity of the systemcan be calculated by equation 4, where 132.16 g/mol is the paraldehydemolecular weight.

$\begin{matrix}{{189.5\mspace{14mu}{\frac{kJ}{mol} \div 132.16}\mspace{14mu}\frac{g}{mol} \times 1000\mspace{14mu}\frac{g}{kg}} = {1,434\mspace{14mu}\frac{kJ}{kg}}} & (4)\end{matrix}$

The 1,434 kJ/kg is the maximum theoretical cold energy storageachievable. The depolymerization and vaporization processes operate inthe temperature range of 4-45° C., under pressure applied in a range of3-12 pound per square inch absolute (psia); in the embodimentshereinafter described, pressure from a blower is applied in the range of4-9 psia.

After depolymerization, acetaldehyde gas can be re-polymerized toparaldehyde liquid over an acid catalyst. The polymerization process(acetaldehyde to paraldehyde) operates in the temperature range of26-55° C., under pressure ranges from 10 to higher than 14.7 psia; inthe embodiments herein described, pressure from a blower is applied inthe range of 10-25 psia,

Shown in FIGS. 2-4 are schematic process flow diagrams of embodiments ofthe disclosed technology, including an apparatus that includes coldenergy storage, having three distinct assemblies in liquidcommunication: a depolymerization assembly 100, a polymerizationassembly 200, and cold energy storage assembly 300. In these embodimentsthe depolymerization assembly 100 includes a DCU 101, a PSU 102, aliquid pump 103, and a blower 104. The polymerization assembly 200includes a PHU 201. The cold energy storage assembly 300 includes a daystorage tank (DST) 301, a polymer cooling unit (PCU) 303 and acold-energy storage tank (CST) 302. Each of the DCU 101 and the PHU 201of the assemblies are configured as heat exchangers, wherein catalyticreactions occur and heat is exchanged. The PSU 102 and the PCU 303 arealso configured as heat exchangers, although no catalytic reaction isintended in these tanks. The DST 301 and CST 302 are all storage tanks,not intended to be significant heat exchangers. The tanks and vesselsshould be made from materials that are compatible with the selectedsystem polymer and its monomer; stainless steel is a suitable materialfor these tanks and vessels. The DCU 101 and the CST 302, and other heatexchanger vessels and tanks of the embodiments of the disclosedtechnology may be wrapped in heat insulation, designed as double walledtanks, or may otherwise be insulated from ambient air conditions.

The configuration of the heat exchanger tanks 101, 102, 201, and 303 maybe independently configured to maximize heat transfer and obtain theright temperature at the flows' exit. The DCU 101 and the PSU 102 areheat exchangers designed to receive source liquid, and transfer heattherefrom to the respective depolymerization and separation reactionswithin the tanks. Liquid to multiphase fluids heat exchangers, such asshell and tube heat exchangers, with straight or coiled tubes, counteror parallel flow, single or double pass, are all suitable heatexchangers to accomplish this heat transfer; other heat exchangers mayalso be suitable for purposes of these reactors of the disclosedtechnology. The DCU 101 contains an acid based catalyst in the polymerflow portion of the reactor.

The PSU 102 may be a vapor-liquid separator designed with the inletmixtures from the DCU 1003 and the PHU 1009 to be separated to monomerrich vapor 1005 (greater than 80 wt % monomer, and in some embodimentsgreater than 90 wt % monomer gas) and polymer rich liquid 1004 (greaterthan 80 wt % polymer, and in some embodiments greater than 90 wt %polymer liquid), under the applications' pressure and temperatureconditions. A pressure regulating valve 106 is used to control theamount of mixture from PHU 201 to PSU 102 so that the pressuredifference between the two units is properly maintained at the rangesdescribed hereinabove. Other vapor-liquid separator designs including,but not limiting to, fractionation and distillation column design, canalso be employed in the PSU to provide high separation efficiency andeffectiveness. In some embodiments, a level control mechanism such as afloat level switch is used to allow the accumulation of the polymer richliquid at the bottom of the PSU; when the level is reached, the PSUoutlet port is opened and the accumulated polymer rich liquid stream isdischarged from the PSU.

The PHU 201 may be configured as an air-to-gas/multiphase heatexchanger, such as a tube and fin heat exchanger, with an acid basedcatalyst in the monomer/polymer flow portion of the reactor. The PCU 303may be configured as an air-to-liquid heat exchanger, such as a tube andfin heat exchanger. Other heat exchanger configurations may be suitablefor purposes of these reactors of the disclosed technology.

The embodiment of FIG. 5 includes an uninterrupted cooling cycleapparatus, without cold energy storage. The components and operatingparameters of this embodiment are similar to the components in theafore-described system having cold energy storage, but without the largestorage tanks of the cold energy storage assembly. Specifically, in thisembodiment the rich liquid polymer mixture is stored in a much smallerpolymer storing tank (PST) 105, and then pumped to the DCU 101,providing uninterrupted cooling cycle operations. The PST may be sizedto hold about one-half of the polymer needed for one cycle through thesystem of the present disclosure.

In some embodiments, as shown in FIG. 8, the system comprises two ormore PSUs, for example with a first PSU 102 positioned after the DCU101, receiving streams of monomer rich vapor, and by its heat exchangerconfiguration further separating out monomer gas from polymer gas beforeconveying the vapor to the PHU 201, and a second PSU 202 positionedafter the PHU 201, receiving streams of polymer rich liquid, and furtherseparating out monomer liquid (which evaporates in PSU 202 to monomergas) therefrom before conveying the polymer rich liquid to the PST 105or the DCU 101. The polymer rich liquid from the first PSU 102 and thesecond PSU 202 in this embodiment may then be conveyed to the PST 105for later depolymerization by the DCU, and the monomer gas from thefirst PSU 102 and the second PSU 202 may be conveyed back to the PHU forpolymerization. A second blower 204 may also be provided to activelyremove monomer gas from the PSU 202. In this embodiment, either ambientair or condenser cooling water may be used to supply heat to the PSUs102, 202.

In these embodiments source liquid 1001, 1006, such as coolant water isconveyed to the DCU and the PSU(s) by means of an external pump (notshown), such as the cooling water pump of the condenser. The flow rateof the source liquid through the heat exchanger tubes can be controlledby means of the pump so that the temperature of the source liquid upondischarge from the DCU tube is near or at the optimum temperature of theturbine (35-52° C.).

Inlet and outlet ports or valves may be positioned within the system ofthe disclosed technology to control fluid flow. The pumps used inassociation with or as part of the system of the disclosed technologymay be controlled by a pump control system, which may receive signalsfrom sensors within the DCU and the PSU, for example, and other heatexchangers, tanks and lines of the disclosed technology, to pumpadditional source liquid through the DCU or the PSU, additional polymerinto the DCU, additional monomer rich gas from the DCU, and deliverpolymer liquid to the CST, or from the CST to the PCU, or otherwisecontrol the flow of liquids and vapor through the system of thedisclosed technology to reach the desired source liquid temperature andoptimize operation of the system.

The DCU 101 is an endothermic reactor, with a heat transfer surface (atits tubes, for example) allowing the reaction process to absorb heatfrom the source liquid cycled into the DCU tubes at 1001. The conversionfrom a polymer to a monomer liquid and the vaporization of the monomerliquid occur over a catalyst in the polymer coolant flow portion of thereactor; because this reaction is endothermic, it absorbs asignificantly large amount of heat from the circulating source liquid,at the heat transfer surface. The polymer may be continuously cycledinto the DCU vessel at 1008 l when ambient temperatures makesupplemental cooling desirable, the cool liquid polymer stored in theCST 302 is pumped into the DCU 101 from the stream 1011. A monomer richvapor mixture is withdrawn from the DCU vessel at 1003, under a lowpressure effect provided by the blower 104. This depletion of themonomer in the DCU forces the depolymerization reaction to promotefurther polymer depolymerization in reaching chemical equilibrium. Forparaldehyde, depolymerization and vaporization occurs at any temperatureat or above 4° C.; operating temperatures of 10-45° C. within the DCUappear to maximize depolymerization and vaporization. Flow rate of theparaldehyde into the DCU at 1008 in the range of 20-39 grams/minute,under pressure in the range of 4-9 psia, results in a cooling rate of0.3-1.0 kW. The temperature of the source liquid as it exits the DCU at1002 may be controlled by the flowrate of the source liquid, the polymerfeed rate and the rate of withdrawal of the monomer rich vapor.

In the embodiments shown in FIGS. 2-5, under the influence of blower104, the monomer rich vapor mixture (A(g) and Pa(g)) flows first to PSU102, in stream 1003. The blower applies pressure to the tanks of thedepolymerization assembly (and the cold storage assembly of FIGS. 2-4)in the range of 4-9 psia, to cause monomer gas separation and activeremoval of the monomer rich vapor from each of the DCU and the PSU. Theblower exit pressure is in the range of 10-25 psia, forcing the vapormixture from the PSU to flow into the PHU.

In these embodiments, the PSU 102 also acts as a buffer tank between theDCU 101 and the PHU 201, minimizing the impact of the sudden change inambient conditions on the DCU operation, and allowing the system tooperate continuously with no material imbalance. In the PSU 102, furtherseparation of the monomer gas from the polymer gas occurs, using anindependent stream of source liquid 1006, 1007 as the heat source, andfurther adding more cooling capacity to the system (wherein the streamof source liquid exiting the PSU may be mixed with the cooler sourceliquid exiting the DCU, or may be circulated through the DCU for furthercooling). Specifically, the heat from the source liquid separatesmonomer gas and polymer liquid. The flow of condenser cooling water as asource liquid may be achieved by the condenser pump, and regulated tocontrol the heat provided thereby within the PSU. The separated monomerrich stream then flows to the PHU 201, under the pumping pressures ofthe blower 104, in flow streams 1005 and 1010. The temperature of stream1010 is intended to be close to ambient temperature. In some embodimentsanother heat exchanger is placed before the PHU to cool stream 1010 tonear ambient temperatures, thereby limiting the reaction temperature inthe PHU.

In the PHU 201, the monomer gas (A(g)) is polymerized over an acidcatalyst to a polymer rich liquid (Pa(I)). The acid catalyst may beprovided in a spherical (bead) form, packed inside of the heat exchangeras a packed bed reactor. Supporting metal screens or perforated matedplates may be positioned at both ends of the heat exchanger tube(s) tohold the catalyst bed in place, while allowing the monomer to flowthrough the catalyst bed. In the embodiment, where the polymer isparaldehyde, acetaldehyde is polymerized back to paraldehyde, over acatalyst, at a temperature range between about 40-60° C., and a pressurerange between 10 and 25 psia.

This polymerization over an acid catalyst is an exothermic process,where the temperature of the monomer and polymer increases above ambienttemperature. Heat is expelled at 1014 from the PHU to the ambientenvironment at a heat transfer surface. In some embodiments the PHU heatexchanger consists of multiple finned tubes, with ambient air beingblown across the surface of the finned tubes. The fins on the tubeincrease heat transfer surface area and allow efficient heat rejectionfrom the PHU to the atmosphere. A fan can be configured to either blowor pull air across the PHU for efficient heat removal at 1014.

In the embodiments shown in FIGS. 2-5, the PHU produces a polymer richliquid mixture which flows back to the PSU 102 in flow stream 1009. Thepressure differential between the PHU 201 and PSU 102 is regulated byblower 104 in the path of flow stream 1005, 1010 as hereinabovedescribed, and through a pressure regulating valve 106 or an orifice, apump, or a combination of all or any of these devices, in the path offlow stream 1009. By means of the circulating plant condenser coolingwater 1006, 1007, the PSU heat exchanger further vaporizes monomer gasfrom the polymer rich liquid mixture, and a more concentrated polymerrich liquid stream is then expelled from the PSU to the DST 301 (or asshown in FIG. 5, directly back to the PST 105 to the DCU 101), in flowstream 1004. In some embodiments (for example, see FIG. 8) a second PSUis provided for this separation of monomer gas from the polymer richliquid mixture, wherein the monomer gas is evaporated from the liquidand recirculated through the PHU 201.

It is noted that the monomer rich gas from the depolymerization assemblycomprises up to 20%, or in some embodiments less than 10%, polymer gas;likewise, the polymer rich liquid from the polymerization assemblycomprises up to 20%, or in some embodiments less than 10%, monomerliquid. The PSU(s) further separate the monomer from the polymer, ineach of these states.

In the embodiment shown in FIGS. 2, 3 and 4, if necessary to cool theliquid polymer at night for next day operation, the liquid polymer isstored in the DST 301 and when the ambient air is cooler is pumped bypump 103 to PCU 303, by stream 1011 to 1012. The PCU 303 cools theliquid paraldehyde using the colder night ambient air, expelling heat at1015. The cooled liquid paraldehyde then flows to the CST 302 forstorage, in flow stream 1013, and is ready for the next day operationand/or conveyance to the DCU by streams 1011 to 1008.

Programmable three-way valves may be used to control the flow pattern ofthe polymer rich liquid through and from the cold energy storageassembly, including for example (a) from the CST 302 to the DCU 101(during the day's high ambient temperature), (b) from the DST 301 to thePCU 303 and CST 302 (during the cooler night ambient temperatures), (c)from the DST 301 to the DCU 101 (when the CST 302 is depleted, or theambient temperature is not too high for the depolymerization reaction),or (d) to control the liquid pump 103 discharge flow either to the DCU101 or PCU 303. Additional valves may be provided throughout the systemto control fluid flow, such as for example, between the PHU and the PSU.

The catalyst within the DCU and the PHU may be the same or differentacid based catalysts (except when used in a heat pump, as hereinafterdescribed, wherein the catalysts must be the same), suitable forpolymerization or depolymerization of the selected polymer. It isbelieved that most strong acid based catalysts would be suitable for usein the process of the disclosed technology. Examples of strong acidbased catalysts suitable for use with the polymer paraldehyde includeperflurosulfonic acid and sulfonic acid, such as Amberlyst 47, Amberlyst15, Amberlyst, Amberlite, Amberjet, Purolite, Nafion NR and NickleSulfate. The catalyst resin (in all or some of the catalytic heatexchangers) may be acid, silica or activated carbon based. Favorablefunctions in a selected catalyst are high reaction rate with theselected polymer and high coefficient of heat transfer. Packingmaterial, such as metal, may be incorporated into the resin bed to allowthe use of less catalyst and maximize the heat transfer area within atank.

As an example, Table 1 indicates the flow rate, temperature, pressure,enthalpy, composition and phases for the streams defined in FIG. 4. Thethermodynamic states were calculated for a 100 MW_(th) cooling plant andrepresent the conditions for steady state operation of the system.

TABLE 1 Comparison of Heat Capacity and Energy Use Units 1011 1008 10031005 1010 1009 1004 1013 1001 1002 Phase [—] Liquid Liquid Vapor SatVapor Sat. Sat. Liq Liq Liq Vapor Liquid Liq. Quality [kg Vap./ 0.0 0.01.0 1.0 1.0 1.0 0.0 0.0 0.0 0.0 kg Liq.] X_(Ac) [massf 0.1 0.1 — — — 0.20.1 0.1 0.0 0.0 liq.] X_(H2O) [massf 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 1.01.0 liq] Y_(Ac) [massf — — 0.9 0.9 0.9 — — — — — vap] Flow [kg/s] 82.282.2 82.2 95.8 95.8 95.8 82.2 82.2 2,234 2,234 Rates Temp. [° C.] 38.038.0 30.0 30.0 62.0 39.0 40.0 38.0 40.0 30.0 Pressure [psi] 7.4 7.4 7.47.4 13.0 13.0 7.4 7.4 31.5 29.1 Enthalpy ×10³ −5.07 −5.07 −3.94 −3.94−3.90 −5.01 −5.1 −5.1 −15.9 −15.9 [kJ/kg]

FIG. 2 shows a flow diagram of an embodiment of the disclosed technologyas used for cooling the condenser cooling water in a power plant; FIG. 3shows a flow diagram of an embodiment of the disclosed technology asused as the condenser in a power plant.

In another embodiment of the disclosed technology, as shown in theschematic process flow diagram of FIGS. 6 and 7, a reversible heat pumpspace cooling and heating cycle apparatus and method is provided. Inthis embodiment two heat exchangers 401 and 501 are provided todepolymerize and polymerize the polymer/monomer conveyed through thesystem, in the traditional heat pump evaporator assembly 400 andcondenser assembly 500. The components of this embodiment are similar tothe components in the dry cooling embodiment without cold energy storagedescribed above, with an expansion device 408 and several control valves405, 406 and 407, wherein the heat exchanger 401 and the PSU 402 (at2001/2002) are air-to-liquid or to-multiphase heat exchangers.

As shown in FIG. 6, in the cooling mode the heat exchanger 401 of theevaporator assembly 400 functions as a depolymerization cooling unit, inliquid communication with a PSU 402, a polymer storing tank (PST) 403, aliquid pump 404, two two-way automatic control valves 406 and 407, andexpansion valve 408. The automatic control valve 406 provides expansionvalve functions when the flow is directed towards the PSU 402. In thismode the heat exchanger 501 of the condens407 reverer assembly functionsas the polymerization heating unit, in liquid communication with a 3-wayautomatic control valve 503. Polymer and its depolymerized monomer flowamong the heat exchangers 401 and 501, with a PSU 402 further separatingthe monomer and polymer, as described in the embodiments above, by flowlines 2003, 2005, 2006-a, 2008, 2004 and 2007-a. A blower, compressor orvacuum-pump 502 is provided to actively remove the monomer gas from theheat exchanger 401 and the PSU 402. The blower, compressor orvacuum-pump 502 further generates the pressure ratio between the secondheat exchanger 501 and the PSU 402. The pressure in the second heatexchanger 501, in the cooling mode, is regulated by a pressureregulating valve, orifice, pump or a combination of all of these devices408. Thereby, as air 2001 flows past the heat exchanger 401 and the PSU402, it is cooled by the depolymerization of the polymer over a catalystand evaporation of the monomer, and transferred to the heat exchanger501 at 2006-a, wherein heat 2011 from the heat exchanger 501 is expelledto the environment.

In the heating mode (shown in FIG. 7), the flow is reversed, and thefirst heat exchanger 401 functions as the polymerization heating unit(providing an exothermic reaction of the monomer over a catalyst), andthe second heat exchanger 501 functions as the depolymerization coolingunit (providing an endothermic reaction of the polymer over a catalyst).Valves 503, 405, 406 and 407 reverse the flow of the polymerimonomer, sothat polymer and monomer flow among the heat exchangers 401 and 501 byflow lines 2004, 2005, 2006-b, 2007-b, 2008 and 2009. The blower 502 isprovided to actively remove the monomer gas from the heat exchanger 501and the PSU 402. In the heating mode, the pressure between the firstheat exchanger 401 and the PSU 402 is regulated through either apressure regulating valve, orifice, pump or a combination of all ofthese devices 408. Thereby, as air 2001 flows past the heat exchanger401, it is heated by the polymerization of the monomer over a catalyst,and heat from the environment 2010 and the PSU 402 at 2002 is drawn inby heat exchanger 501, in its depolymerization endothermic reaction, andcool air is expelled at 2011.

In another embodiment of the disclosed technology, as shown in FIG. 9,water is incorporated into an uninterrupted cooling cycle apparatuswithout cold energy storage, similar to the embodiment shown in FIG. 5.In this process water is fed into the system of the disclosed technologyto inhibit formation of side products or undesired compounds, such as2-butenal (Crotonaldehyde). 2-butenal is formed by aldol condensation ofacetaldehyde (Ac) where the two acetaldehyde molecules link together andform a carbon-carbon bond with the removal of a water molecule. In thepresence of a strong acid catalyst, similar to the acid catalysthereinabove described in the disclosed technology, the acetaldehydefirst forms nucleophilic enol, followed by an acid catalyzed dehydrationreaction (loss of water molecule) to form 2-butenal. Although thereaction pathway is in favor of the reversible reaction between polymerand monomer, small percentage of the 2-butenal can be formed where enoldehydration favors. During the depolymerization of the paraldehyde ofthe methods of the disclosed technology, wherein produced 2-butenal maybe produced as an intermediate species in the formation of the longerchain polymers. These undesired compounds have the potential to reducethe polymer coolant concentration over long term operation, resulting ina long term coolant stability issue.

Water was found to be an effective 2-butenal inhibitor in thedepolymerization cycle operation and has low solubility with the polymercoolant. In the present embodiments, adding water content up to 10 wt %reduces 2-butenal concentration to zero. In the embodiment shown, thewater is co-fed with the polymer into the DCU 101. As shown in theembodiment of FIG. 9, the water and polymer are co-fed into the DCU 101by replacing the PST 105 of the embodiment shown in FIG. 5 with aliquid-liquid separation/storage tank (LST) 107, to facilitateindependent feeding of both water at feed stream 1012 and paraldehydepolymer at feed stream 1008 to the DCU 101, by means of liquid pumps 108and 103, respectively, from the LST 107. Water and the polymer arestored in the LST 107 as two distinct layers, with the water layer inthe bottom and the polymer layer in the top of the tank, due to thedensity difference between water and the polymer, and the low solubilityof water in the polymer.

Further, in the embodiment shown in FIG. 9, the system of FIG. 5 isfurther modified so that the water and polymer are co-fed at or near thetop portion of the DCU 101. By such configuration, the accumulation ofwater in the DCU 101 (resulting from the low solubility between thewater and paraldehyde, and the slightly higher density of water thanparaldehyde) is avoided. This further allows for optimumdepolymerization rates, higher chemical conversion, and higher coolingrate.

In this embodiment of FIG. 9, when operating in a cooling process boththe polymer and the water are pumped from the LST 107 to the top of theDCU 101, entering the DCU as a combined stream of water and polymer. Thepolymer is pumped in stream 1008, and the water is pumped in stream1012. The pumping rates of the two pumps 103 and 108 are controlled tomaintain appropriate water content in the feed by up to 10 wt % and toproduce a uniform mixture of water and polymer.

As in previously described embodiments of the disclosed technology, thepolymer is depolymerized in the DCU 101 into a monomer, such asacetaldehyde. In this embodiment, the water also flows through the DCU101, without any chemical reaction with the polymer, the monomer or thecatalyst. However, due to the low pressure effects in the DCU 101 at 4-9psia, partial evaporation of water (up to 5 wt %) occurs. Theevaporation results in a monomer rich vapor mixture that consists ofA(g), Pa(g), and water vapor. Under the low pressure effect provided bythe blower 104, water, polymer liquid, and the monomer rich vaporstreams continuously exit from the bottom of the DCU 101 entering PSU102 in flow stream 1003.

The PSU 102 and polymerization assembly 200 will operate similarly asdescribed in other embodiments. In the PSU 102, the monomer and watervapor, up to 5 wt %, are separated from the liquid polymer and liquidwater and flow to the blower 104 in stream 1005, then pumped to the PHU201 in stream 1010. Subsequently, water will be in the PHU 201 andstreams 1009 and 1013. The small water content will not alter theoperations of the components other than inhibiting the side reactionthat forms the 2-butenal in the PHU 201.

The polymer rich stream (Pa(I), A(I), and water) exits the PSU 102 inflow stream 1004 to the LST 107. The mixed stream is separated in theLST 107 into the water layer in the bottom and the polymer layer in thetop of the tank. The recovered water and polymer rich stream are thenpumped to the DCU 101 to repeat the cooling cycle of the disclosedtechnology.

FIG. 10 shows the application of this incorporation of water into thesystems of the disclosed technology as applied to the heatpumpembodiment of FIG. 6, operating in a cooling cycle. In this embodimentthe system is composed of two main assemblies: Evaporator Assembly 400and Condenser Assembly 500. Under cooling mode, the heat exchanger 401functions as a depolymerization cooling unit. The heat exchanger 401 isin liquid communication with a PSU 402, a paraldehyde liquid pump 404, a3-way valve 405, a water liquid pump 410, and an LST 409. The automaticcontrol valve 407 controls the flow of the depolymerization productsdirected to the PSU 402 in stream 2003. In this operating mode, the heatexchanger 501 of the condenser assembly 500 operates as thepolymerization heating unit, in liquid communication with a 2-way valve408 and a three-way valve 503. A paraldehyde and water mixture in stream2007-a is introduced into the depolymerization unit 401. The mixtureundergoes an endothermic depolymerization and evaporation process,drawing heat from stream 2001 and decreasing its temperature to that ofstream at 2002. The water in stream 2007-a does not react inside 401,but experiences partial evaporation. Stream 2005 consists of avapor-liquid mixture, rich in acetaldehyde; its flow from the DCU 401into the PSU 402 in stream 2003, and its flow rate is controlled byvalve 407. The PSU 402 separates the streams 2003 and 2008 (from thePHU) into a vapor stream 2005, rich in acetaldehyde, and a liquidparaldehyde and water stream 2004. As hereinabove described, the LST 409separates the paraldehyde and water in stream 2004, into a liquid waterstream 2009 and a paraldehyde stream 2012. The liquid pumps 404 and 410control the paraldehyde and water flow rate, respectively. The blower,compressor or vacuum pump 502 generates a pressure difference betweenthe evaporator assembly 400 and the condenser assembly 500, by which thewater vapor is condensed into liquid water. The liquid polymer andliquid water also flow to the PSU 402. Furthermore, it facilitates theevaporation of stream 2005 and its flow into PHU 501 where it undergoesa polymerization and condensation process. Heat generated in PHU 501 isdissipated to the system surroundings into stream 2010, resulting in adischarge air stream 2011. The liquid products from the polymerizationprocess in PHU 501 are discharged through stream 2008, its flow rate iscontrolled by one 2-way expansion valve 408. After undergoing anexpansion process, stream 2008 flows into the PSU 402 and undergoes thepreviously explained separation process,

FIG. 11 shows the application of this incorporation of water into thesystems of the disclosed technology as applied to the heatpumpembodiment of FIG. 7, operating in heating mode. As indicated by streams2006-b and 2007-b, the flow direction in the system is changed. Underthis configuration the heat exchanger 401 functions as the PHU and theheat exchanger 501 as the DCU. The flow direction is modified using two3-way valves 405 and 503. The liquid paraldehyde and water are reroutedby 405 and co-fed into the DCU 501 in stream 2007-b. The heat exchanger501 draws heat from air stream 2010 decreasing its temperature to thatof stream 2011. The depolymerization products exit the DCU 501 in stream2008 into the PSU 402. The blower, compressor or vacuum-pump 502 drawsthe vapor rich stream 2005 from the PSU 402. The vapor stream out of theblower, compressor or vacuum-pump 502 is redirected by one 3-way valve503 into stream 2006-b and enters the heat exchanger 401. Polymerizationreaction and condensation processes take place in the heat exchanger401, dissipating heat into stream 2001 and increasing its temperature tothat of stream 2002. The dissipated heat is also used in the evaporationprocess in the PSU 402.

Although not shown, water may be similarly incorporated into theembodiments of the disclosed technology shown in FIGS. 2-4 and 8.

The potential impact of the dry-cooling system of the disclosedtechnology for cooling power plant condenser cooling water is theperformance penalty imposed by air cooling when ambient temperatures arehigh. The performance penalty is the result of higher temperaturecooling water returning to the condenser, raising condenser saturationpressure and lowering turbine output. In contrast, wet cooling allowscooling systems to operate at wet bulb temperature levels. Under similarcondition, the web bulb temperature is lower than the dry bulbtemperature, by an average of 3-5° C. As a result of this fundamentalthermodynamic limitation, the use of prior art dry cooling systemsresult in an average of 2% loss of power output from the steam turbinecompared to wet cooling operation, and up to 10% reduced powerproduction under high ambient temperature conditions.

The system and methods of the disclosed technology eliminates the powerproduction loss (performance penalty) due to high ambient temperaturespresent in traditional dry cooling technology. Further, the disclosedtechnology is a closed system, with zero water dissipation to theatmosphere, while providing cooling below ambient dry bulb temperature.The disclosed technology thereby provides a transformational anddisruptive development compared to the traditional cold storagetechnologies, such as ice storage and room temperature phase changematerials (PCMB). The system of the disclosed technology, with itspractical 1,363 kJ/kg heat storage capacity, has 4 times the heatstorage capacity of ice and 7 times the capacity of PCM systems, anduses significantly less energy than comparable technologies (see Table2). These qualities lead to a smaller and cost effective cooling system,

TABLE 2 Comparison of Heat Capacity and Energy Use PureTemp (EntropySalt Ice Disclosed Phase Change Material Solutions) Paraffin HydratesStorage Technology Source Vegetable Petroleum Minerals Water PolymerAverage Heat Storage, kJ/kg 170-270 130-170 140-170 334 up to 1,330Energy Use in kWh/kWh Stored n/a n/a n/a ~1.3 ~0.04

With prior art technology, the dry bulb ambient air temperature and thesecond law of thermodynamics set the lower limit of the steamcondensation temperature within an air-cooled condenser. High ambienttemperature excursions penalize power plant power output performance.The system of the disclosed technology provides an innovative solutionto cool below ambient dry bulb temperature limit and address temperatureexcursions. The novel approach of combining depolymerization andre-polymerization to create a cycle that pumps heat from a power plantcooling system to the atmosphere effectively eliminates extensive wateruse and lowers the amount of energy required to provide cooling waterfor efficient turbine energy production. Likewise, certain reversiblechemical reactions which produce endothermic and exothermic reactionswithin the condenser and ambient temperature ranges may be used in lieuof the depolymerization and polymerization reactions hereinabovedescribed. When standalone or combined with current dry coolingtechnology (with other technology operating at ambient temperatureswithin 5° C. higher than the power plant design point), the system ofthe disclosed technology has the potential to make thermoelectric powerplants independent from the nation's water supply infrastructure,operate with high efficiency, and conserve significant water resourcesfor use in the agricultural, municipal, and industrial sectors.

The system of the disclosed technology can also serve other industrialcooling applications such as closed cooling loops for gas turbine inletair cooling, lube oil cooling, steam cracker cooling for polymerproduction, and intercooling loop for large industrial compressors, aswell as other applications as hereinabove described.

The invention claimed is:
 1. A dry-cooling system useful in absorbingheat from a source liquid, the system comprising a depolymerizationcooling unit (DCU) in fluid communication with a polymerization heatingunit (PHU), wherein: the DCU comprises a DCU heat exchanger, wherein thesource liquid cycles through the DCU; wherein a first acid basedcatalyst is disposed within the DCU, and the DCU receives a polymerliquid and water; wherein contact of the polymer over the first catalystwithin the DCU causes an endothermic reaction, converting the polymer toa monomer gas, wherein the endothermic reaction causes at least aportion of the water to vaporize into water vapor, and wherein theendothermic reaction further draws heat from the source liquid as thesource liquid cycles through the DCU, and wherein the DCU expels themonomer gas and water vapor; and the PHU comprises a PHU heat exchanger,wherein a second acid based catalyst is disposed within the PHU, and thePHU receive the monomer gas and the water vapor, wherein flow of themonomer gas over the second acid based catalyst causes an exothermicreaction, converting the monomer gas to the polymer liquid, and whereinthe exothermic reaction generates heat which is rejected from the systemthrough the PHU, and wherein the PHU expels the polymer liquid and thewater for conveyance to the DCU.
 2. The dry-cooling system of claim 1,the system further comprising a liquid to liquid separator and a pair ofpumps, in fluid communication between the PHU and the DCU, to separatethe polymer liquid from the water, and convey the polymer liquid and thewater expelled from the PHU to the DCU.
 3. The dry-cooling system ofclaim 1, further comprising a blower in fluid communication with the DCUand the PHU, wherein the blower is designed and configured to withdrawthe monomer vapor and water vapor from the DCU, under pressure ofbetween about 4 to 9 psia, and convey the monomer vapor and water vaporto the PHU under pressure of between about 13 to 25 psia.
 4. Thedry-cooling system of claim 1, wherein the polymer is paraldehyde. 5.The dry-cooling system of claim 1, wherein the first acid based catalystand the second acid based catalyst are the same.
 6. The dry-coolingsystem of claim 1, the system further comprising a first polymerseparation unit (PSU) in fluid communication between the DCU and thePHU, wherein: the PSU comprises a PSU heat exchanger, wherein the sourceliquid cycles through the PSU, wherein the PSU receives from the DCU themonomer gas and water vapor, which stream also comprises a polymer gas,wherein heat from the source liquid is transferred to the polymer gas,monomer gas and water vapor, to further separate the monomer gas fromthe polymer gas, and liquefy the polymer gas, and wherein the PSU expelsthe monomer gas to the PHU.
 7. The dry-cooling system of claim 6,wherein the PSU further receives from the PHU the polymer liquid, amonomer liquid and water, and wherein heat from the source liquid istransferred to the polymer liquid, the monomer liquid and the water, tofurther separate the polymer liquid from the monomer liquid, andvaporize the monomer liquid to the monomer gas, and wherein the PSUexpels the polymer liquid and the water for conveyance back to the DCU.8. The dry cooling system of claim 7, further comprising a cold energystorage assembly comprising a day storage tank (DST), a polymer coolingunit (PCU) and a cold-energy storage tank (CST), wherein: the DST is influid communication with the first PSU to receive the polymer liquid,and with the PCU to expel the polymer liquid, the PCU comprises a PCUheat exchanger, and receives from the DST the polymer liquid, and expelsthe cooler polymer liquid from the PCU, and the CST is in fluidcommunication with the PCU to receive the cooler polymer liquid, and isfurther in fluid communication with the DCU for expelling the coolerpolymer liquid to the DCU.
 9. The dry-cooling system of claim 8, furthercomprising: a pump in fluid communication between the PSU, the DST andthe DCU, a three-way valve in fluid communication with the pump, whichthree-way valve directs flow of the polymer liquid among the PSU, DCU,DST, PCU and CST.
 10. The dry-cooling system of claim 6, furthercomprising a second PSU in fluid communication between the PHU and theDCU, wherein: the second PSU receives from the PHU the polymer liquid, amonomer liquid and water, wherein heat from the source liquid istransferred to the polymer liquid, the monomer liquid and water, tofurther separate the polymer liquid from the monomer liquid, andvaporize the monomer liquid to the monomer gas; and wherein the secondPSU expels the polymer liquid and water for conveyance back to the DCU.11. A method for a dry-cooling system useful in absorbing heat from asource liquid, the method comprising the steps of: providing a polymer,water and a source liquid; in a first heat exchanger through which thesource liquid flows, converting the polymer to a monomer vapor over afirst catalyst, causing an endothermic reaction over the catalyst, theendothermic reaction drawing heat from the source liquid and causing thewater to vaporize into a water vapor; withdrawing the monomer vapor andwater vapor from the first heat exchanger; in a second heat exchanger influid communication with the first heat exchanger, receiving the monomervapor and water vapor and converting the monomer vapor to a polymerliquid over a second catalyst, causing an exothermic reaction over thecatalyst, the exothermic reaction expelling heat through the heatexchanger to an environment; and discharging the polymer liquid and thewater from the second heat exchanger back to the first heat exchanger.12. The process of claim 11, wherein the source liquid is power plantcondenser water.
 13. The process of claim 11, wherein the source liquidis exhausted steam from power plant steam turbine last stage.
 14. Themethod for a polymerization cycle of claim 11, further comprising thesteps of in a third heat exchanger through which the source liquid alsoflows, receiving the monomer vapor from the first heat exchanger and thepolymer liquid from the second heat exchanger, and further separatingthe monomer gas from the polymer liquid, using the source liquid as aheat source; discharging the polymer liquid to the first heat exchanger,and discharging the monomer vapor to the second heat exchanger.
 15. Themethod for a polymerization cycle of claim 14, further comprising thesteps of: in a first tank, receiving the polymer liquid from the thirdheat exchanger before it is delivered to the first heat exchanger; in afourth heat exchanger, receiving the polymer liquid from the first tankand flowing air past the fourth heat exchanger to lower the temperatureof the polymer liquid; in a second tank, receiving and storing thecooler polymer liquid from the fourth heat exchanger; and dischargingthe stored cooler polymer liquid to the first heat exchanger.
 16. Amethod for cooling a source liquid, the method comprising: in a firstheat exchanger through which a source liquid flows, depolymerizing apolymer in an endothermic reaction, thereby drawing heat from the sourceliquid and producing a monomer gas, and vaporizing water to form a watervapor; withdrawing the monomer gas and the water vapor from the firstheat exchanger; in a second heat exchanger, polymerizing the monomer gasand condensing the water vapor, producing the polymer and the water; anddelivering the polymer and the water to the first heat exchanger.
 17. Aheat pump, comprising: a polymer, a catalyst and water; a first heatexchanger and a second heat exchanger, wherein the first and second heatexchangers are designed and alternatingly configured to process eitheran endothermic reaction or an exothermic reaction over the catalystdisposed within each of the heat exchangers, to produce respectiveproduct streams, and are further designed to vaporize water to watervapor during the endothermic reaction, and to condense the water vaporto the water during the exothermic reaction; a polymer separation unit(PSU) in liquid communication with the heat exchangers, where theproducts streams are received and separated; a blower in liquidcommunication with the heat exchangers and the PSU to actively remove amonomer gas from the heat exchanger processing the endothermic reaction;and a plurality of pumps and a plurality of valves to generate anddirect flow of the products through the heat exchangers, the PSU and theblower.
 18. A heat pump, comprising: a polymer and a catalyst; a firstheat exchanger and a second heat exchanger, wherein the first and secondheat exchangers are designed and alternatingly configured to processeither an endothermic reaction or an exothermic reaction over thecatalyst disposed within each of the heat exchangers, to producerespective product streams; a polymer separation unit (PSU) in liquidcommunication with the heat exchangers, where the products streams arereceived and separated; and a plurality of pumps and a plurality ofvalves to generate and direct cyclical flow of the products through theheat exchangers and the PSU.